TCL Error on replacing strings

Hi everyone,

Trying to understand what might be the issue with replacing content with regsub, getting following error :

<HTTP_REQUEST> - ERR_ARG (line 2)    invoked from within "HTTP::uri [regsub "/3dnotification" [HTTP::uri] ""] "

I might replace the regsub with other operand doing the same operation.

The iRule code is the following :

   if { not ( [string tolower [HTTP::uri]] starts_with "/socket.io" )} then {

      HTTP::uri [regsub "/3dnotification" [HTTP::uri] ""]

      # need to strip trailing slash on URI otherwise results in 404 for resources...

      HTTP::uri [regsub "\/$" [HTTP::uri] ""]

   } elseif { [string tolower [HTTP::header Upgrade]] contains "websocket" } {

      ONECONNECT::reuse disable

      set oc_reuse_disable 1

   }

   HTTP::header replace "X-Forwarded-ContextPath" "/"

}